The induction of tolerance in B cells will be investigated in an in vitro system in which helper T cells and macrophages are provided and suppressor T cells do not contribute to the induction of tolerance. The role of IgM and IgD in tolerance induction will be studied by examining the tolerability of cell populations purified with regard to the isotype they bear using the fluorescent activated cell sorter and also by removing or blocking these recptors by means of specific divalent or univalent antibody respectively. Populations enriched in antigen-specific cells will be obtained by immunoabsorbent techniques and tolerized by antigens that are or can be detected by fluorescent, radioactive or density labels. This will facilitate analysis of the fate of tolerized cells including subcellular changes, macromolecular synthesis and the fate of cell surface antigen-receptors and other surface markers. By correlating these changes with induction of tolerance, it is hoped to determine the cell surface events critical to tolerance induction and the behavior of the tolerized B cell. An attempt will be made to study the affinity of cell surface IgM and IgD by purifying these respective isotypes from plasma membrane fractions and subjecting them to radioimmunoassay and equilibrium dialysis.